Realizing discrete growth of thin Li2O2 sheets on black phosphorus quantum dots-decorated δ-MnO2catalyst for long-life lithium–oxygen cells

Abstract

Lithium–oxygen (Li–O2) cells have attained increasing attention in recent years due to their extremely high energy density. An efficient catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a key factor for high-performance Li–O2 cells. In this work, a unique design of catalytic cathode composed of black phosphorus quantum dots-decorated δ-MnO2 nanobelts (BPQD/δ-MnO2) on carbon cloth is proposed. The thin belt-like architecture of δ-MnO2 and porous structure of the catalytic cathode not only provide numerous catalytic sites for ORR/OER but also facilitate transportation of the reactants and deposition of the discharge product. The synergic effect of δ-MnO2 and BPQD enables discrete growth of thin Li2O2 sheets on δ-MnO2, leading to high capacity (8463 mAh g−1 at 100 mA g−1) and long cycle life (182 cycles at 400 mA g−1 with a limited capacity of 1000 mAhg−1) of the cells. Density functional theory calculations support that Li2O2 favors conformal growth on δ-MnO2 in the presence of BPQD.